Why is Diagnosis Important?
The history and physical examination are the basis for diagnostic hypothesis generation; the first step in the diagnostic process. Accurate diagnosis precedes the three tasks central to the healing professions: explanation, prognostication, and therapy. These three tasks have been consistently performed by physicians throughout time and across cultures, regardless of the belief system or theory underpinning the practice: magic, faith, rationalism, or science. They provide answers to the patient’s three fundamental questions: (1) What is happening to me and why? (2) What does this mean for my future? (3) What can be done about it, how will that change my future? [Cohen JJ. Remembering the real questions. Ann Intern Med. 1998;128:563–566; Kravitz RL, Callahan EJ. Patients’ perceptions of omitted examinations and tests: A qualitative analysis. J Gen Intern Med. 2000;15:38–45].
Failure to pursue a diagnosis may permit a disease to progress from curable to incurable. On the other hand, for many complaints, in otherwise healthy people with no alarm symptoms or signs, a good prognosis can be ascertained without knowing the exact cause of the complaint, as, for instance, an upper respiratory infection. The experienced clinician can reassure the patient that further testing is unnecessary and will not change prognosis or treatment. It takes experience, knowledge of the medical literature, good judgment, and an understanding of the fundamentals of clinical epidemiology and decision making to determine when pursuit of specific symptoms and signs is warranted. For an excellent review of the principles of epidemiology in a highly readable format, see Fletcher et al. [Fletcher RH, Fletcher SW, Fletcher GS. Clinical Epidemiology, the Essentials. 5th ed. Baltimore, MD: Lipincott, Williams & Wilkens; 2012].
Diseases and Syndromes: Communication and Entry to the Medical Literature
For thousands of years, physicians have recorded recurring patterns of disordered bodily structure, function, and mentation that suggest a common cause. Each pattern receives a specific name. When a common etiology and pathophysiology are confirmed, we designate the condition a disease. Other clusters of attributes, known by a combination of features not clearly related to a single cause, are called syndromes. Diseases and syndromes are intellectual constructs allowing the physicians to study groups of patients with relatively homogeneous physiologic disorders; they do not exist independently of the patients who manifest them. The diagnosis of a disease or syndrome provides an entry to the medical literature to obtain information about etiology, diagnostic findings, treatment, and prognosis.
An accurate diagnosis is indispensable to offering your patients evidence-based therapy, that is, therapy validated in clinical trials based upon accurate diagnosis of participating subjects who are similar to your patient.
The Diagnostic Examination
To reach accurate and comprehensive diagnoses the clinician must catalog each abnormality of the patient’s anatomic structure, physiologic function, and mentation. Every disease has a temporal sequence of clinical ...